This invention relates to an improved riser for an irrigation sprinkler and more particularly to an improved biasing arrangement for such a riser for urging the riser to its normally retracted position and for retaining it in a vertical position when it has popped up.
As is well known, there are a wide variety of inground sprinkler systems that employ a housing that is adapted to be buried within the ground and which supports a riser for movement from a retracted position to an extended sprinkling position. A wide variety of spray heads are carried by the risers for irrigating and/or watering the surrounding terrain when the riser pops up under water pressure. Although such devices offer considerable convenience, there are certain disadvantages to the prior art types of construction which have rendered them less than fully suitable for their intended purpose. For example, the sliding support between the riser and its housing should be such that it will not be prone to sticking when grass, the soil or materials that are added in granular form to the soil for purposes such as fertilizing, insect or weed control or the like become lodged within the housing. In addition, the riser should be capable of substantial movement between its retracted position and its extended sprinkling position so as to insure good water distribution when the riser pops up.
In order to obviate certain of the aforenoted disadvantges, it has been proposed to provide a sprinkler of the type generally described wherein a flexible diaphragm is interconnected between the supporting housing and the riser. Such a diaphragm serves the combined purpose of providing a seal between the housing and the riser and also can function to provide the support for the riser and its movement between its retracted and its storage position. Although such diaphragm type arrangements can offer some advantages, those which have been proposed in the prior art are not fully effective to achieve their intended purpose. For example, a conventional diaphragm cannot have sufficient resilience to permit the desired degree of movement and also so as to insure retraction of the riser when water pressure is not present. For this reason, it has been proposed to employ helper springs or retraction springs for retracting the riser when it is not in use. However, consistent with maintaining a compact overall size, the type of spring arrangements previously employed have not served their intended purposes. Either they have sufficient force so as to effect retraction and, accordingly, restrict the overall movement or they will permit the necessary degree of lift for the riser and then do not have sufficient force to insure good retraction and smooth movement throughout the entire range of travel. Also, the spring arrangements previously employed have not offered sufficient force and direction of force application to hold the riser in a vertical position when extended.
It is, therefore, a principal object of this invention to provide an improved riser for a pop up type irrigation sprinkler.
It is a further object of this invention to provide a riser that will have substantial movement and which embodies an effective retraction spring that permits such large degrees of movement and holds the riser in a vertical position when extended.
It is a further object of this invention to provide an improved retraction spring arrangement for a pop up type of riser.